4,527 research outputs found
Low-noise top-gate graphene transistors
We report results of experimental investigation of the low-frequency noise in
the top-gate graphene transistors. The back-gate graphene devices were modified
via addition of the top gate separated by 20 nm of HfO2 from the single-layer
graphene channels. The measurements revealed low flicker noise levels with the
normalized noise spectral density close to 1/f (f is the frequency) and Hooge
parameter below 2 x 10^-3. The analysis of the noise spectral density
dependence on the top and bottom gate biases helped us to elucidate the noise
sources in these devices and develop a strategy for the electronic noise
reduction. The obtained results are important for all proposed graphene
applications in electronics and sensors.Comment: 9 pages, 4 figure
Invariant Criterion for the Design of Multiple Beam Profile Emittance and Twiss Parameters Measurement Sections
We introduce and give examples of applications of an optimality criterion
which can be used for the design and comparison of multiple beam profile
emittance and Twiss parameters measurement sections and which is independent
from the position of the reconstruction point.Comment: 3 pages, IPAC1
Relations between Projected Emittances and Eigenemittances
We give necessary and sufficient conditions that two sets of positive real
numbers must satisfy in order to be realizable as eigenemittances and projected
emittances of a beam matrix. The information provided by these conditions sets
limits on what one can to achieve when designing a beam line to perform
advanced emittance manipulations.Comment: 3 pages, IPAC1
Possibilities for reduction of transverse projected emittances by partial removal of transverse to longitudinal beam correlations
We show that if in the particle beam there are linear correlations between
energy of particles and their transverse positions and momenta (linear beam
dispersions), then the transverse projected emittances always can be reduced by
letting the beam to pass through magnetostatic system with specially chosen
nonzero lattice dispersions. The maximum possible reduction of the transverse
projected emittances occurs when all beam dispersions are zeroed, and the
values of the lattice dispersions required for that are completely defined by
the values of the beam dispersions and the beam rms energy spread and are
independent from any other second-order central beam moments. Besides that, we
prove that, alternatively, one can also use the lattice dispersions to remove
linear correlations between longitudinal positions of particles and their
transverse coordinates (linear beam tilts), but in this situation solution for
the lattice dispersions is nonunique and the reduction of the transverse
projected emittances is not guaranteed.Comment: 13 pages, 2 figure
- …